Hello! My name is Dr. Aida and I am glad to attend you on Healthcaremagic! Oxetol is an antiepilepsy drug, used to treat focal or secondary generalized seizures. It should be used for a long time (at least three years after the last seizure), regularly. It is true that forgetting to take it, can trigger seizures. Regarding the adverse effects, it can lead to allergic reaction, dizziness, double vision, agitation, abdominal pain, etc.. But as your brother has been taking it without these adverse effects, it seems that he is tolerating it well. Hope you will find this information helpful! Best wishes!